Joe Biden debated well. He demonstrated a clear breadth and depth of knowledge, and when he was discussing issues, he backed up his points well. Put simply, he adhered to the first principle of debating: substantiate your argumentation with evidence. He pretty much took a sledgehammer to the claims of the McCain campaign, and not just with rhetoric but with actual facts and analysis. The kind of stuff you can go and check for yourself to make an informed decision. Fundamentally, he showed that he knows what he is on about, that he has an awareness of the important contemporary issues, and that he knows what the job demands. Lest I sound like an Obama campaign shill, all of these points stand regardless of your stance on the positions Biden himself took. You don't need to agree with him to be able to say that he presented clear arguments in favour of Obama/himself and against McCain/Palin, and sustained this argumentation with evidence. You could come back and say that he misinterprets or misrepresents the evidence, but he undeniably performed well; he debated the actual issues and represented his side articulately and with substance.
Sarah Palin didn't debate. There are thousands of inept and unqualified politicians out there, but Palin is surely at the very top of the heap. Quite simply, Palin is completely out of her depth. Regardless of the issue, she seemed completely incapable of sustaining an argumeent through evidence. Regardless of the issue, she seemed to considerably lack knowledge, awareness, or expertise. She even showed a stark lack of understanding of the position she is running for, in how the vice presidential position relates to the executive and the legislature, or for that matter what the executive actually does. At times, she even admitted to her ignorance and tried to distort this into a virtue as a "Washington outsider"; she is much less a Washington outsider and much more a competence outsider. Basic concepts of governance elude her. Basic concepts of debating are lost on her. She thunderously demonstrated that even when she is not making hilarious gaffes, she is thoroughly inept and incapable. She is dangerously unqualified. The best she can muster is irrelevant "folksy" rambling devoid of substance. She cannot address a topic, she cannot support her positions, she cannot refute the claims of the Obama campaign - again, regardless of whether or not you agree with her (though it is hard to agree with somebody seemingly unable to articulate and substantiate a clear stance on anything), these points stand independently. Sarah Palin is grossly unqualified and ignorant.
The debate was a mismatch and a complete walkover. Sure, Palin didn't gift the world another hilarious gaffe, but her best was not even faintly good enough and she resoundingly lost.